Effects of hypoxia on the intercellular channel activity of cultured glomus cells

Dual voltage clamp experiments have shown that hypoxia induced by Na-dithionite or N2 reduced junctional macroconductance (Gj) in about 70% of cultured and coupled glomus cell pairs while increasing it in the rest. To explore possible mechanisms for these effects, we studied the activity of gap junction channels under similar conditions. The calculated single channel conductances (gj) fell into two categories. A low-conductance group, which was most frequently observed, had a mean gj of 27.8 +/- 0.29 pS (mean +/- SEM; n = 968 events). The other group had higher conductances (47.6 +/- 0.35 pS; n = 528). When PO2 was reduced (hypoxia), the low conductances did not change significantly in any of the junctions. The high-conductance units appeared less frequently in some junctions whereas in others they remained unaltered. Thus, rapid channel flickering during hypoxia may not be the only mechanism determining Gj during coupling or uncoupling. It is possible that slow (seconds) opening and closing of the channels could play an important role in this phenomenon.